Why don't you just go with a 2 stroke like you rode? Maintenance is cheaper, a 250 is plenty big for you, and its a bit more of a challenge to ride. Personally, when I rode a friend's CRF150, I was a bit bored, being your size, compared to my other friend's RM 250. I bought myself an RM 250 and I don't think I'll be outgrowing it any time soon. Look into KTM, Husqvarna, or GasGas if you look into two strokes, They are pretty much the most reliable ones out there and are great for trails while still dominating on the track. 2 strokes are way more fun to ride, in my opinion. Hitting that powerband and clicking through gears is alot of fun for me.